KR20120028933A - Copper zinc tin chalcogenide nanoparticles - Google Patents

Abstract

The present invention relates to nanoparticles of casterite (copper zinc tin sulfide) and copper zinc tin selenide nanoparticles, inks and devices thereof, and methods of making the same. Nanoparticles are useful in absorber layers as p-type semiconductors in thin film solar cell applications.

Description

Copper zinc tin chalcogenide nanoparticles {COPPER ZINC TIN CHALCOGENIDE NANOPARTICLES}

This application claims 35 U.S.C. Claiming priority under §119 (e) from US Provisional Application Nos. 61 / 180,179, 61 / 180,181, 61 / 180,184, and 61 / 180,186, and claiming their benefits;

Each of which was filed on May 21, 2009, each of which is incorporated herein in its entirety as part of it for all purposes.

The present invention relates to copper zinc tin chalcogenide nanoparticles, compositions thereof, and their use in thin films and devices. Nanoparticles are p-type semiconductors useful for absorber layers in solar cells.

Solar cells and solar modules, also called photovoltaic or PV cells, convert sunlight into electricity. These devices use the specific electronic properties of semiconductors to convert the sun's visible and near-visible energy into available electrical energy. This conversion is due to the absorption of radiant energy in the semiconductor material and liberates some valence electrons, resulting in electron-hole pairs. As used in the art, the terms “band gap energy”, “optical band gap” and “band gap” are necessary to generate electron-hole pairs in semiconductor materials. Energy, generally the minimum energy required to excite an electron from a valence band to a conduction band.

Solar cells have traditionally been fabricated using silicon (Si) as a light-absorbing, semiconducting material in relatively expensive manufacturing processes. To make the solar cell more economically viable, the solar cell device structure is made of thin films such as copper-indium-gallium-sulfo-di-selenide, Cu (In, Ga) (S, Se) ₂ , also called CIGS. In addition, light-absorptive semiconductor materials have been developed for low cost use. This class of solar cells typically has a p-type absorbent layer sandwiched between a back electrode layer and an n-type junction partner layer. The back electrode layer is often Mo, while the junction partner is often CdS. Transparent conductive oxides (TCO), such as but not limited to zinc oxide doped with aluminum, are formed on the junction partner layer and are typically used as transparent electrodes. CIS-based solar cells are said to have power conversion efficiencies in excess of 19%.

The development of nanocrystalline CIGS and the production of films therefrom have been reported in many papers and patent applications. For example, WO 08/021604 discloses chalcopyrite by reacting a metal component with an elemental chalcogenide precursor in the presence of an alkylamine solvent having a normal boiling point above about 200 ° C. and an average particle size of about 5 nm to about 1000 nm. ) To prepare nanoparticles. The reaction temperature varied from 265 ° C to 280 ° C. WO 99/037832 discloses a method of forming a film of metal chalcogenide semiconductor material on a substrate from a colloidal suspension comprising metal chalcogenide nanoparticles and a volatile capping agent. Colloidal suspensions are prepared by reacting metal salts with chalcogenide salts to precipitate metal chalcogenides, recover metal chalcogenides and mix metal chalcogenides with volatile capping agents, while WO 09/051862 Disclosed is a semiconductor thin film (including its ink) formed from nonspherical particles.

Despite the mentioned potential of CIGS in thin film solar cells, the toxicity and low abundance of indium and selenium are major obstacles to the widespread use and tolerance of CIGS in commercial devices. An alternative to the absorber layer of thin film solar cells is copper zinc tin sulfide, Cu ₂ ZnSnS ₄ (CZTS). It has a direct band gap of about 1.5 eV and an absorption coefficient greater than 10 ⁴ cm ^-1 . In addition, CZTS does not contain any toxic or nonabundant elements. While the crystals of CIGS have a chalcopyrite structure, the CZTS crystals are enclosed in a kesterite structure against the chalcopyrite structure by being doubled along the c-axis.

Currently, the development of solar cells based on CZTS is far behind CIGS-based solar cells. Although the first CZTS heterojunction PV cell was reported in 1996, the current write efficiency for the CZTS cell is 9.6%. Currently, thin films of CZTS are available for sputtering Cu, SnS, and ZnS precursors, hybrid sputtering, pulsed laser deposition, spray pyrolysis of halides and thiourea complexes, electrodeposition / thermal sulfurization, E-beam Cu / Zn / Sn Has been prepared via thermal sulfiding, sol-gel and then thermal sulfiding and via printed precursors. Dissolved Cu-Sn chalcogenide (S or S-Se),

Hybrid solution-particle approaches to CZTS have been reported involving the preparation of Zn-chalcogenide particles, and hydrazine-based slurries comprising excess chalcogen. Hydrazine is a highly reactive and potentially explosive solvent described in the Merck Index as a "violent poison."

Accordingly, there remains a need for the development of improved CZTS particles and compositions, films and devices made therefrom.

In one embodiment, provided herein are quaternary nanoparticles containing copper, zinc, tin, chalcogen, and capping agents, wherein the chalcogen is selected from the group consisting of sulfur, selenium, and mixtures thereof.

In another embodiment, provided herein are compositions containing a plurality of quaternary nanoparticles containing copper, zinc, tin, chalcogens, and capping agents, wherein the chalcogens are sulfur, selenium, and mixtures thereof. Selected from the group consisting of:

In a further embodiment, in the present invention there is provided a composition containing a plurality of quaternary nanoparticles containing copper, zinc, tin, chalcogen, and a capping agent and an ink containing an organic solvent, wherein the chalcogen is Sulfur, selenium and mixtures thereof.

In yet another embodiment, provided herein is a film made from a composition containing a plurality of quaternary nanoparticles containing copper, zinc, tin, chalcogen, and a capping agent, wherein the chalcogen is sulfur, Selenium and mixtures thereof. In yet another embodiment, an electronic device containing the film described above in the present invention is provided.

In yet another embodiment, the reaction mixture of (a) metal salts and / or complexes of (i) copper, zinc and tin, (ii) one or more chalcogen precursor (s), and (iii) a capping agent Forming in a solvent, and (b) heating the reaction mixture to form nanoparticles, provides a method for producing copper-zinc-tin-chalcogenide quaternary nanoparticles.

In yet another embodiment, in the present invention, a layer of a composition containing a plurality of quaternary nanoparticles containing copper, zinc, tin, chalcogen, and a capping agent is deposited on a substrate (where chalcogen is sulfur , Selenium and mixtures thereof); A method of forming a film is provided by drying the deposited layer of the composition and removing solvent therefrom.

The present invention addresses the need for the development of environmentally sustainable nanocrystalline semiconductors and inks of such semiconductors, based on highly natural richness and low toxicity elements. Moreover, there is a need for thin films and devices based on such materials. Particular preference is given to nanocrystalline, environmentally sustainable semiconductors useful in the manufacture of thin film absorber layers suitable for use in solar cells, in view of the reduced supply of fossil fuels and increased global energy requirements. Also particularly preferred are nanocrystalline materials that can be annealed at lower temperatures. During nanoparticle synthesis, appropriate reaction temperatures, short reaction times, and minimal steps in isolation and purification are desirable to reduce costs, conserve energy, and develop commercially viable processes. Synthesized reaction mixtures can utilize reagents and solvents with relatively low toxicity and can act as ink or ink precursors, with nanoparticle synthesis processes without isolation or purification steps particularly preferred.

Moreover, nanocrystalline semiconductors, and synthetic pathways to such nanoparticles, allow such nanosize particles to have many unique physicochemical properties such as quantum size effects, size-dependent chemical reactivity, optical non-linearity, and efficient photoelectron emission. It is interesting because Films of nanocrystalline semiconductors can act as precursor films for absorber layers in thin film solar cells with significantly lower annealing temperatures than films made from larger particles. Beyond the inherent energy savings associated with reduced thermal budget, the reduced deposition temperature allows the use of lower cost substrates such as soda lime glass and potentially even polymer-based substrates, while substrates This dissipation is alleviated and thermal stress is alleviated.

Various features and / or embodiments of the invention are illustrated in the drawings as described below. These features and / or embodiments are merely representative, and the selection of these features and / or embodiments included in the drawings is not subject to the subject matter of the invention, which is not included in the drawings, is suitable for practicing the invention. The subject matter not included in the figures shall not be construed as an indication that they are excluded from the scope of the appended claims and their equivalents.
<Figure 1>
1-1, 1-2, 1-3 and 1-4 show transmission electron microscopy (“TEM”) of nanoparticles prepared in Example 1. FIG.
<FIG. 2>
2 shows the TEM of nanoparticles prepared in Example 2. FIG.
3,
3 shows a perspective view of a stack of layers in a solar cell.
<Figure 4>
4 shows performance data for the film as prepared in Example 15. FIG.

The present invention is referred to in certain embodiments by the term “CZTS”, which includes quaternary nanoparticles containing copper, zinc, tin and sulfur and / or selenium, which may be a compound such as Cu ₂ ZnSnS ₄ . Examples of other compounds included herein include "CZTSe" called Cu ₂ ZnSnSe ₄ ; "CZTS / which includes all possible combinations of Cu ₂ ZnSn (S, Se) ₄ , including Cu ₂ ZnSnS ₄ , Cu ₂ ZnSnSe ₄ and Cu ₂ ZnSnS _x Se _4-x , where 0 ≦ x ≦ 4. Se ". Accordingly, the term "CZTS", "CZTSe" and "CZTS / Se" Sn is _{1 .3} copper zinc tin sulfide / selenide semiconductor, for example, the formula Cu Zn _{1 .94 0 .63} having various stoichiometric S ₄ It includes those described by. That is, the stoichiometry of the element is not strictly limited to the ratio of 2 Cu: 1 Zn: 1 Sn: 4S / Se (ie, the molar ratio of copper to zinc to tin to chalcogen is about 2: 1: 1: 4). . In other embodiments, the molar ratio of Cu / (Zn + Sn) may be less than 1.0, or the molar ratio of zinc to tin may be greater than one. In low copper CZTS solar cells, for example, even if the molar ratio of Cu / (Zn + Sn) is less than 1.0, a molar ratio of more than 1 zinc to tin is often preferred for high efficiency devices. The compounds may also be doped in small amounts of various dopants selected from the group consisting of binary semiconductors, elemental chalcogens, sodium, and mixtures thereof.

CZTS is crystallized with the casterite structure and has a casterite structure, where "casterlight" refers to a substance belonging to the minerals of the casterite and stannite strains. Casterlite is a mineral name that refers to a crystalline compound in an I4- or I4-2m space group having the nominal chemical formula Cu ₂ ZnSnS ₄ . However, other metals, such as Fe, replace Zn. When a large number of Zn is substituted by Fe, this is called stanite. The casterite is once present in the form of Zn and I4- on Cu and 2d (1 / 2,0,1 / 4) on 2a (0,0,0) and 2c (0,1 / 2,1 / 4) positions. Although thought to be Zn, Zn can occupy the Cu position and on the contrary represents a disorder in which Cu can occupy the Zn position, which has been shown to degrade the identity for I4-2m. The difference in cation order is indistinguishable by x-ray diffraction due to the similarity of x-ray scattering factors for Cu and Zn. This can be distinguished by neutron diffraction. The material produced by this pathway provides a diffraction pattern consistent with the casterite structure and containing peaks that are distinct from monosulfide and oxide. Similarly, X-ray absorption spectroscopy (XAS) is unique to casterite forms and reveals spectral features that are distinguishable from monosulfides and oxides. In the case of XAS, fractions of Cu and Zn atoms in the casterite phase are obtained. Depending on the overall elemental stoichiometry this allows the determination of the ratio of Cu to Zn in the casterite phase. This is clearly distinguished from mixtures of individual sulfide phases which produce the same elemental ratio in the aggregates. Minerals of the casterite and stanite strains are further discussed from sources such as Hall, SR et al, Canadian Minerologist, 16 (1978) 131-137.

In one embodiment of the invention, there is provided nanoparticles containing copper, zinc, tin and chalcogens, wherein the chalcogens are selected from the group consisting of sulfur, selenium and mixtures thereof. As used herein, the term "chalcogen" refers to a group 16 element, and the term "metal chalcogenide" or "chalcogenide" refers to a semiconductor material consisting of a metal and a group 16 element. As used herein, the term "binary-metal chalcogenide" refers to a chalcogenide composition comprising one metal. The term "ternary-metal chalcogenide" refers to a chalcogenide composition comprising two metals. The term "quaternary-metal chalcogenide" refers to a chalcogenide composition comprising three metals. The term "multi-metal chalcogenide" refers to a chalcogenide composition comprising two or more metals and includes ternary and quaternary metal chalcogenide compositions. Metal chalcogenides are useful candidates for photovoltaic applications because many of these compounds have good optical bandgap values in the ground solar spectrum.

The particles of copper, zinc, tin and chalcogen provided herein are nanoparticles having a longest dimension of about 1 nm to about 1000 nm. As used herein, the terms “nanoparticle”, “nanocrystal” and “nanocrystalline particle” are used interchangeably to include spheres, rods, wires, tubes, debris, whiskers, rings, discs, and triangles. Particles having various shapes and crystalline structures, which are characterized by the longest dimension of from about 1 nm to about 1000 nm, preferably from about 5 nm to about 500 nm, and most preferably from about 10 nm to about 100 nm. Where the prefix "nano" refers to a size (as mentioned above) within the nanoscale. The longest dimension of a nanoparticle is defined as the measurement of the nanoparticle from end to end along the longest dimension, which dimension will depend on the shape of the particle. For example, for a spheroidal or substantially spheroidal particle, the longest dimension will be the diameter of the circle as defined by the particle. For other irregularly shaped particles (eg, crystals that may have a polygonal shape), the longest dimension may be a diagonal or facet that causes the longest dimension to be the longest distance between any two points on the surface of the particle. Methods for determining the longest dimension of nanoparticles are described in "Nanoparticles: From Theory to Application", G. Schmid, (Wiley-VCH, Weinheim, 2004); And sources such as "Nanoscale Materials in Chemistry", K. J. Klabunde, (Wiley-Interscience, New York, 2001). In some specific embodiments of the invention, the shape of the nanoparticles provided herein is triangular.

In another embodiment thereof, provided nanoparticles of copper, zinc, tin and chalcogen may incorporate a capping agent herein, which may be a group or ligand that is physically absorbed or adsorbed or chemically bound to the surface of the particle. Can be. The capping agent functions as a type of monolayer or coating on the particles and can act as a dispersing aid. When the ligand functions as a capping agent, the metal complex is often formed such that the metal is bound to a peripheral array of molecules or anions. Atoms in ligands that are directly attached to a central atom or ion are called donor atoms and often include nitrogen, oxygen, phosphorus or sulfur. Ligands donate at least one electron pair to a metal atom. Examples of capping agents suitable for use herein include any one or more of the following:

(a) organic molecules containing functional groups such as nitrogen-, oxygen-, sulfur-, or phosphorus-based functional groups;

(b) Lewis bases; In various embodiments, the Lewis base may be selected to have a boiling point of at least about 150 ° C. at ambient pressure and / or may be selected from the group consisting of organic amines, phosphine oxides, phosphines, thiols, and mixtures thereof;

(c) a group that can be converted to an electron pair-donating group, or an electron pair-donating group and has a boiling point of less than about 150 ° C. at ambient pressure;

(d) primary, secondary or tertiary amine groups or amide groups, nitrile groups, isonitrile groups, cyanate groups, isocyanate groups, thiocyanate groups, isothiocyanate groups, azide groups, thio groups, Thiolate group, sulfide group, sulfinate group, sulfonate group, phosphate group, phosphine group, phosphite group, hydroxyl group, alcoholate group, phenolate group, ether group, carbonyl group and carboxylate group;

(e) carboxylic acid, carboxylic anhydride, and glycidyl group; Ammonia, methyl amine, ethyl amine, butylamine, tetramethylethylene diamine, acetonitrile, ethyl acetate, butanol, pyridine, ethanethiol, tetrahydrofuran, and diethyl ether;

(f) a solvent in which nanoparticles are formed, such as oleylamine; And / or

(g) amines, amides, nitriles, isonitriles, cyanates, isocyanates, thiocyanates, isothiocyanates, azides, thiocarbonyls, thiolates, sulfides, sulfinates, sulfonates, phosphates, phosphines, A member selected from the group consisting of phosphites, hydroxyls, alcoholates, phenolates, ethers, carbonyls, carboxylates, carboxylic acids, carboxylic anhydrides, glycidyls and mixtures thereof.

In yet another embodiment, the present invention provides a composition containing a plurality of nanoparticles as described above. Such compositions can have a particle size distribution such that, for example, the average longest dimension of the particles is in the range of about 10 nm to about 100 nm and the standard deviation is about 10 nm or less.

Nanoparticles as provided herein can be prepared in a reaction mixture in a solvent such as an organic solvent. Suitable organic solvents include Lewis bases, and organic solvents capable of forming Lewis bases. The purpose of the solvent is to provide a medium for the reaction and to help minimize or prevent agglomeration of the nanoparticles. Suitable organic solvents that act as both solvents and capping agents include solvents having Lewis basic functional groups. Lewis basic solvents are useful for that purpose because they often, but not always, succeed in providing a coordinating media that covers the surface of the nanoparticles and prevents the nanoparticles from agglomerating. Some particular classes of suitable organic solvents include organic amines, phosphine oxides, phosphines and thiols. Preferred solvents are alkyl amines, more preferably from the group consisting of dodecylamine, tetradecyl amine, hexadecyl amine, octadecyl amine, oleylamine, and trioctylamine, with oleylamine being particularly preferred. Solvents suitable for use herein include those having a boiling point of at least about 150 ° C. at ambient pressure. For example, Lewis base solvents having a boiling point of at least about 150 ° C. at ambient pressure are also useful, and the group consisting of organic amines, phosphine oxide, phosphine and thiols more preferably has a boiling point of at least about 150 ° C. at ambient pressure. And alkyl amines having a boiling point of at least about 150 [deg.] C. at ambient pressure.

Metal salts and / or complexes of copper, zinc and tin are used as sources of copper, zinc and tin. These may include copper complexes, zinc complexes, and tin complexes of one or more organic ligand (s). Suitable metal salts and / or complexes also include complexes and salts of copper (I), copper (II), zinc (II), tin (II) and tin (IV) with organic and / or inorganic counterions and ligands. do. Particular preference is given to metal salts and / or complexes comprising copper (I), copper (II), zinc (II), tin (II) and tin (IV) halides, acetates, and 2,4-pentanedionate. Suitable chalcogen sources or precursors are elemental sulfur, elemental selenium or mixtures. An advantage of using elemental chalcogen as a chalcogen source is that it facilitates the use of the reaction mixture itself as an ink or ink precursor without further purification. Copper (I), copper (II), zinc (II), tin (II) and tin (IV) complexes with organic ligands are preferred for applications in which the reaction mixture will be used as an ink or ink precursor. Copper (I), copper (II), zinc (II), tin (II) and tin (IV) complexes of acetate and 2,4-pentanedionate are particularly preferred for this application.

Other suitable copper salts and / or complexes include copper (I) halides, copper (I) acetates, copper (I) 2,4-pentanedionates, copper (II) halides, copper (II) acetates, and copper (II) Those selected from the group consisting of 2,4-pentanedionate; Zinc salts and / or complexes are selected from the group consisting of zinc (II) halides, zinc (II) acetate, and zinc (II) 2,4-pentanedionates; Tin salts and / or complexes include tin (II) halides, tin (II) acetates, tin (II) 2,4-pentanedionates, tin (IV) halides, tin (IV) acetates, and tin (IV) 2, 4-pentanedionate is selected from the group consisting of.

As mentioned above, the term "metal complex" as used herein refers to a composition in which a metal is bound to a peripheral array of molecules or anions, and is typically referred to as "ligand" or "complexing agent". Atoms in ligands that are directly attached to a central atom or ion are called donor atoms and often include nitrogen, oxygen, phosphorus or sulfur. Ligands donate at least one electron pair to a metal atom. As used herein, the term “complex of one or more organic ligand (s)” refers to a metal complex comprising one or more organic ligands, including metal acetate and metal acetylacetonate, which is also referred to as “2,4-pentanedionate” do. The term "metal salt" refers to a composition in which metal cations and inorganic anions are conjugated by ionic bonds. Suitable classes of inorganic anions include oxides, sulfides, carbonates, sulfates and halides.

A heating mantle, heating block, or oil / sand bath can be used to heat the flask containing the reaction mixture. Alternatively, heating can be performed using electromagnetic radiation. A magnetic stirrer is usually placed inside the flask to allow the reaction mixture to mix well. Optionally, after synthesis, nanoparticles can be separated from reaction by-products and non-ligated solvents via precipitation with one or more nonsolvents or antisolvents. Preferred antisolvents for the precipitation of nanoparticles are organic protic solvents or mixtures thereof, with methanol and ethanol being particularly preferred.

In another embodiment of the process, the individual metal salts of copper, zinc and tin are dissolved separately in a solvent such as oleylamine to form a solution. The solution is mixed to form a mixture, which is maintained at about 100 ° C. A solution of elemental chalcogens such as sulfur in the solvent is added to the mixture. The temperature is raised to 230 ° C. where the reaction color changes from light brown to black, indicating the formation of nanoparticles. The reaction heating is stopped after 10 minutes and the system is left to cool for 1 hour. The reaction is then stopped using an organic polar protic antisolvent such as ethanol or a mixture of solvent and antisolvent and the solution is centrifuged. Solids are collected by moving to the bottom of the tube and decanting the supernatant. The solid material is resuspended to the desired concentration in a solvent or mixture of solvents.

In another embodiment of the process, the reactant components are added sequentially one after the other. That is, the individual salts or complexes of copper, zinc and tin are dissolved separately in a solvent to form a solution. Elemental chalcogen is dissolved in a solvent to form a chalcogen solution. The tin solution and zinc solution are mixed to form a binary solution. The copper solution is mixed with the binary solution to form a tertiary solution. In the subsequent step, the tertiary solution is heated to 160 ° C. to 230 ° C. under argon. The chalcogen solution is mixed with the tertiary solution at a temperature selected from above to form a quaternary solution. The quaternary solution is then cooled to form copper zinc tin sulfide nanoparticles. Copper zinc tin sulfide nanoparticles are separated from the solvent by adding a nonsolvent such as an organic solvent. The organic solvent may be a polar, protic organic solvent or a binary mixture of polar, protic organic solvents and nonpolar or polar aprotic organic solvents. Copper zinc tin sulfide nanoparticles are separated from the organic solvent by centrifuging and decanting the supernatant.

In another embodiment of the process, the individual metal salts and / or complexes of copper, zinc and tin may be added separately to the mixture of solvent and capping agent in turn to form a reaction mixture, followed by the addition of a chalcogen precursor to the reaction mixture. do. If the solvent and capping agent are present together in the mixture, the capping agent will typically be selected for the Lewis base, and the solvent will typically be selected to be not a Lewis base or to be a Lewis base that binds the nanoparticles less strongly than the capping agent. .

In the present invention, it is advantageous to obtain nanoparticle formation at temperatures lower than typical temperatures, preferably from about 130 ° C. to about 300 ° C., more preferably from about 160 ° C. to about 230 ° C., from about 160 ° C. to About 200 ° C. is most preferred. At about 160 ° C. to about 200 ° C., the procedures described herein frequently provide nanoparticles with the longest dimension in the size range of about 10 nm to about 100 nm. These low temperatures offer the advantage of performing the procedure at or near atmospheric and using lower boiling solvents and capping agents. This will result in less carbon-based impurities in the annealed film. More preferred temperatures of about 160 ° C. to about 230 ° C. are lower than temperatures typically reported for the preparation of metal chalcogenide nanoparticles, resulting in energy savings.

In particular due to the possible formation of metal oxides, it is desirable to prevent oxygen and / or water from being present in the reaction medium during the synthesis of the chalcogenide nanoparticles. Special techniques and equipment are available to achieve an oxygen free atmosphere. As such, the reactant (s) may be prepared, for example, in an oxygen-free atmosphere or in solution (s) in a glove box using a vacuum line or Schlenk line connected to a condenser and a round bottom flask. have. However, if it is inevitable that oxygen is introduced into the system, for example during the addition of the solvent or precursor solution to the reaction flask, an inert gas (eg N ₂ , Ar, for example, to remove oxygen before proceeding with further steps) It may be necessary to purge and / or degas the system with, or He). Although it may be useful to carry out the reaction herein under atmospheric conditions free of oxygen, such an oxygen free environment is not required herein and should not be viewed as limiting the scope of the present teachings, so applicants herein And the formation of CZTS nanoparticles under conditions that limit the presence of water but do not essentially exclude it.

The procedure described herein is characterized by the desired simplicity of the synthetic procedure. More particularly, the disclosed reactions are very fast, so crystalline CZTS nanoparticles form within minutes after the constituent precursor is added. In addition, the synthesis of nanoparticles is carried out at an appropriate temperature near atmospheric pressure. Synthesis tolerates the presence of oxygen. That is, in many cases, the nanoparticles were formed under argon atmosphere, but the precursor solution was prepared in air and did not degas. Moreover, the precursors used for the synthesis of chalcogenide nanoparticles are universally available, low toxicity and easy to handle. Recently, the equipment necessary for the synthesis process is universally available, for example, because no special equipment is required to achieve at high temperatures and pressures.

In yet another embodiment of the invention, the nanoparticles produced by the procedures described herein are highly monodisperse.

The procedure described herein can be used to synthesize quaternary metal chalcogenide CZTS nanoparticles. The CZTS nanoparticles prepared herein comprise crystalline particles having a narrow size distribution which forms a stable dispersion in a nonpolar solvent. Particles as prepared by the procedure were characterized via XRD, TEM, ICP-MS, EDAX, DLS, and AFM. DLS revealed very narrow size distributions (eg 10 ± 10 nm and 50 ± 10 nm) within each category. XRD confirmed the presence of the casterite structure. ICP and EDAX have shown that the continuous addition of reactants and the use of chalcogens as precursors provide more accurate CZTS / Se stoichiometry for reaction conditions using other sources or simultaneous addition of chalcogens such as thiourea.

The process described herein consists of a composition comprising quaternary nanoparticles characterized by a casterite structure and an average longest dimension of about 1 nm to about 1000 nm, or copper, tin, zinc and one or more chalcogen (s). It can be used to prepare a composition comprising quaternary nanoparticles characterized by an average longest dimension of about 1 nm to about 1000 nm.

The procedures described herein can be used to prepare nanoparticles containing copper, zinc, tin, chalcogens and capping agents, wherein the chalcogens are selected from the group consisting of sulfur, selenium and mixtures thereof, and the nanoparticles It has the longest dimension of about 1 nm to about 1000 nm. Another embodiment of the process of the invention features the ability to prepare nanoparticles having one or more of the following features:

Casterite structures;

A molar ratio of copper to zinc to tin to chalcogen that is about 2: 1: 1: 4;

Molar ratio of copper to (zinc + tin) less than 1;

Molar ratio of zinc to tin that is greater than 1;

Longest dimension, about 10 nm to about 100 nm;

Dopants such as sodium are present;

Capping agents include Lewis bases;

The capping agent comprises a Lewis base, wherein the boiling point of the Lewis base at ambient pressure is at least about 150 ° C. and the Lewis base is selected from the group consisting of organic amines, phosphine oxides, phosphines, thiols and mixtures thereof;

Capping agents include oleylamine;

The capping agent has a boiling point of less than about 150 ° C. at ambient pressure and includes groups that can be converted to at least one electron pair-donating group or electron pair-donating group; And / or

Capping agents include amines, amides, nitriles, isonitriles, cyanates, isocyanates, thiocyanates, isothiocyanates, azides, thiocarbonyls, thiolates, sulfides, sulfinates, sulfonates, phosphates, phosphines, Phosphite, hydroxyl, alcoholate, phenolate, ether, carbonyl, carboxylate, carboxylic acid, carboxylic anhydride, glycidyl, and mixtures thereof.

The procedures described herein can also be used to prepare compositions containing multiple nanoparticles as described above, such compositions of nanoparticles can have an average longest dimension of about 10 nm to about 100 nm and the standard deviation is About 10 nm or less.

In another embodiment, the present invention further provides an ink containing CZTS nanoparticles (as described above and / or prepared by the processes described above) and one or more organic solvent (s). In various embodiments, the reaction mixture of starting metal component and solvent may itself be used as ink without further purification. Optionally, after precipitation from the reaction mixture, the nanoparticles can be resuspended at the desired concentration in a solvent or mixture of solvents to provide an ink. Preferred organic solvents include aromatics, alkanes, nitriles, ethers, ketones, esters and organic halides or mixtures thereof, with toluene, p-xylene, hexane, heptane, chloroform, methylene chloride and acetonitrile being particularly preferred. Preferred concentrations of the nanoparticles in the solvent are about 1% to about 70% by weight, more preferably about 5% to about 50% by weight, most preferably about 10% to about 40% by weight.

In addition to CZTS nanoparticles and organic solvents, the ink optionally further comprises dispersants, surfactants, polymers, binders, crosslinkers, emulsifiers, defoamers, desiccants, fillers, extenders, thickeners, film conditioners, antioxidants, glidants, smoothing additives. And one or more chemicals, including but not limited to, corrosion inhibitors, and mixtures thereof. Preferred additives are oligomeric or polymeric binder (s) and mixtures and / or surfactants thereof. Preferably, the oligomeric or polymeric binder is present in an amount of about 20% by weight or less, more preferably about 10% by weight or less, even more preferably about 5% by weight or less, and about 2% by weight or less desirable. These oligomeric or polymeric binders can have a variety of constructs, including linear, branched, comb / brushed, star, highly branched, and / or dendritic architectures.

Preferred classes of oligomeric or polymeric binders preferably include degradable binders having a decomposition temperature of about 250 ° C. or less, more preferably about 200 ° C. or less. Preferred classes of degradable oligomeric or polymeric binders include homopolymers and copolymers of polyethers, polylactides, polycarbonates, poly [3-hydroxybutyric acid], and polymethacrylates. More preferred degradable oligomeric or polymeric binders are poly (methacrylic acid) copolymers, poly (methacrylic acid), poly (ethylene glycol), poly (lactic acid), poly [3-hydroxybutyric acid], poly (DL Lactide / glycolide), poly (propylene carbonate) and poly (ethylene carbonate). Particularly preferred degradable binders include the Elvacite® 2028 binder and the Elbasite® 2008 binder (Lucite International, Inc.). Preferably, the degradable oligomeric or polymeric binder is present in an amount of about 50 wt% or less, more preferably about 20 wt% or less, even more preferably about 10 wt% or less, and about 5 wt% or less. Most preferred.

If present in the nanoparticle ink, the surfactant is preferably present in an amount of about 10% by weight or less, more preferably about 5% by weight or less, and even more preferably about 3% by weight or less and 1% by weight or less. Most preferred. Many surfactants are suitably available for this purpose. Selection may be made based on the coating and dispersion quality observed and / or the desired adhesion to the substrate. In certain embodiments, the surfactants include siloxy-, fluoryl-, alkyl- and alkynyl-substituted surfactants. These include, for example, Bike? Surfactants (Byk Chemie). ), Zonyl? Surfactant (DuPont), Triton? Surfactant (Dow), Surfynol? Surfactant (Air Products) and Die Dynol? Surfactants (air products) are included. Preferred classes of surfactants include cleavable or degradable surfactants and surfactants having a boiling point below about 250 ° C., preferably below about 200 ° C., and more preferably below about 150 ° C. A preferred boiling point surfactant is Sufinol® 61 surfactant from Air Products. Cleavable surfactants are further described in “Cleavable Surfactants”, Hellberg et al, Journal of Surfactants and Detergents, 3 (2000) 81-91; And sources such as "Cleavable Surfactants", Tehrani-Bagha et al, Current Opinion in Colloid and Interface Science, 12 (2007) 81-91.

The ink may optionally further include other semiconductors and dopants. Preferred dopants are binary semiconductors, elemental chalcogens, and sodium. If present in the ink, the dopant is preferably present at about 10% or less, more preferably about 5% or less, and most preferably about 2% or less.

In one particular embodiment, the present invention therefore provides an ink containing a castorite structure and / or nanoparticles characterized by an average longest dimension of about 1 nm to about 1000 nm. In another embodiment, the present invention provides an ink comprising nanoparticles consisting of copper, tin, zinc, one or more chalcogen (s) and a capping agent. Copper, tin, zinc, one or more chalcogen (s) and Nanoparticles composed of a capping agent may also be characterized by the casterite structure and / or the average longest dimension of about 1 nm to about 1000 nm.

In another embodiment, the present invention also provides an ink containing one or more organic solvents with a composition of a plurality of nanoparticles, wherein the nanoparticles in the composition comprise copper, zinc, tin, chalcogens, and capping agents. And the chalcogen is selected from the group consisting of sulfur and selenium. In yet another embodiment, the composition of nanoparticles in the ink, or nanoparticles in the composition, is characterized by one or more of the following features:

Nanoparticles in the composition have a casterite structure;

The nanoparticles in the composition have a molar ratio of copper to zinc to tin to chalcogen that is about 2: 1: 1: 4;

Nanoparticles in the composition have a molar ratio of copper to (zinc + tin) that is less than 1;

The nanoparticles in the composition have a molar ratio of zinc to tin greater than 1;

Nanoparticles have the longest dimension of about 1 nm to about 1000 nm;

The nanoparticles in the composition may be electron pair donor groups, or amines, phosphine oxides, phosphines, thiols, amides, nitriles, isonitriles, cyanates, isocyanates, thiocyanates, isothiocyanates, azides, thiocarbonyls, Can be converted to an electron-pair donor selected from the group consisting of thiolates, sulfides, sulfinates, sulfonates, phosphates, phosphites, hydroxyls, alcoholates, phenolates, ethers, carbonyls, carboxylates, and mixtures thereof. Containing a capping agent having a group present;

The nanoparticles in the composition contain a capping agent that is an oleylamine;

The composition has a particle size distribution characterized by an average longest dimension of about 10 nm to about 100 nm;

The concentration of nanoparticles in the ink is from about 1% to about 70% by weight based on the total weight of the ink;

The organic solvent in the ink is selected from the group consisting of aromatics, alkanes, nitriles, ethers, ketones, esters, organic halides and mixtures thereof;

The inks also consist of dispersants, surfactants, polymers, binders, crosslinkers, emulsifiers, antifoams, desiccants, fillers, extenders, thickeners, film conditioners, antioxidants, glidants, leveling additives, corrosion inhibitors, and mixtures thereof. Containing a component selected from the group;

The ink may be a degradable binder; Degradable surfactants; Cleavable surfactants; Surfactants having a boiling point of less than about 250 ° C .; And one or more binders or surfactants selected from the group consisting of: mixtures thereof;

Inks include homopolymers and copolymers of polyethers; Homopolymers and copolymers of polylactide; Homopolymers and copolymers of polycarbonates; Homopolymers and copolymers of poly [3-hydroxybutyric acid]; Homopolymers and copolymers of polymethacrylates; And one or more degradable binders selected from the group consisting of mixtures thereof; And / or

The ink also contains a dopant selected from the group consisting of binary semiconductors, elemental chalcogens, sodium, and mixtures thereof.

As described above, a composition or ink of nanoparticles may be formed into a film on a substrate, such film may have one or more layers, where some or all of the layers are formed from the ink or composition thereof. The substrate forming the base on which the (s) are to be deposited or disposed may be flexible or rigid. The substrate can be made, for example, from aluminum foil or polymer and then used as a flexible substrate in a roll-to-roll manner (continuous or split) using a commercially available web coating system. Rigid substrates include glass, solar glass, low-iron glass, green glass, soda-lime glass, steel, stainless steel, aluminum, polymers, ceramics, metal plates, metalized ceramic plates, metallized At least one material selected from the group consisting of polymer plates, metallized glass plates, and / or any single or multiple combinations of those mentioned above.

Films of the composition or ink thereof may be wet coated, spray coated, spin coated, doctor blade coated, contact printing, top feed reverse printing, bottom feed reverse printing, nozzle feed reverse printing, gravure printing, microgravure printing, reverse microgravure printing, Any of a variety of solution-based coatings including but not limited to coma direct printing, roller coating, slot die coating, mayerva voting, lip direct coating, dual lip direct coating, capillary coating, inkjet printing, jet deposition, spray deposition, etc. It can be formed on the substrate by the coating of. Other coating techniques useful for film formation include flexo printing, offset printing, screen printing, and heat transfer printing.

Nanoparticles provided by the present invention have semiconductor properties, and unlike conventional semiconductor materials, their nanoparticles tend to interact and aggregate in colloidal suspensions. Incorporation of the capping agent into the nanoparticles is useful to stabilize the colloidal suspension and to prevent its degradation. The presence of the capping agent will help to prevent the interaction and aggregation of the nanoparticles, thereby providing a uniform distribution of colloidal components (e.g., metal chalcogenide nanoparticles), dispersing phases, I will keep it all. Unfortunately, when a nonvolatile capping agent is used, and when a composition or ink of nanoparticles is formed into the film, the nonvolatile capping agent tends to decompose rather than volatilize, thus removing significant impurities (eg, carbon). Introduce into film. Although such impurities are not inherently fatal to film performance, they degrade their electronic properties. In contrast to nonvolatile capping agents, volatile capping agents are typically removed during deposition of the ink to form a film instead of cutting off impurities and introducing them into the film.

An advantage of the present invention is that the use of a suitable reaction temperature as described above allows the incorporation of relatively low boiling capping agents, which are not volatile enough to not be maintained during the reaction to form nanoparticles, but film formation Is sufficiently volatile to be removed during the process. Any capping agent is selected for use during nanoparticle formation, but may be exchanged for a capping agent with greater volatility in further process steps. For example, high boiling nonvolatile capping agents, such as incorporated during nanoparticle synthesis, can be exchanged with volatile capping agents such as volatile coordinating Lewis bases after synthesis of the nanoparticles. Thus, in one embodiment, wet nanoparticle pellets that are stabilized by nonvolatile capping agents as incorporated during synthesis are suspended in volatile capping agents to produce a colloidal suspension in which exchange of capping agents occurs. Next, when the colloidal suspension is deposited on the substrate, it forms a precursor film that is substantially carbon free because the volatile capping agent that replaced the nonvolatile capping agent is released from the suspension during film formation.

In yet another embodiment, the exchange of the capping agent may be effected after film formation. The annealed film may be immersed in a bath in the volatile capping agent, and then the volatile capping agent is as synthesized. Exchanged with a nonvolatile capping agent incorporated into the nanoparticles. The nonvolatile capping agent is then removed with excess volatile capping agent when the film is removed from the bath. The advantages of this method include film densification, with lower levels of carbon-based impurities in the film, especially if the film is subsequently annealed and annealed. Another advantage of this method is that it is relatively insensitive to the presence of water, which can lead to destabilization, aggregation and colloidal degradation of the colloidal suspension.

In yet another embodiment, the reaction mixture of nanoparticles containing the first capping agent is contacted with a second capping agent having greater volatility than the first capping agent to convert the first capping agent into the second capping agent in the nanoparticles. Exchangeable; Or nanoparticles containing the first capping agent are recovered from the reaction mixture to contact the nanoparticles with a second capping agent having greater volatility than the first capping agent to exchange the first capping agent with the second capping agent in the nanoparticles. can do. In yet another embodiment, the film containing the first capping agent is contacted with a second capping agent having greater volatility than the first capping agent to exchange the first capping agent with the second capping agent in the nanoparticles of the film. Can be. In any of the above embodiments, the second capping agent can have a boiling point of less than about 200 ° C. at ambient pressure.

The capping agent in the context of the present invention is considered to be volatile if it is sufficiently volatile if it gradually changes during film deposition instead of decomposing and introducing impurities when the composition or ink of nanoparticles is formed into the film. Capping agents having volatility suitable for use herein are less than about 200 ° C. at ambient pressure, preferably less than about 150 ° C. at ambient pressure, more preferably less than about 120 ° C. at ambient pressure, and most preferably ambient pressure. And those with boiling points below about 100 ° C., each of these ranges being defined at the lower end by non-zero values. Other volatile capping agents suitable for use herein include compounds containing at least one group that can be converted to an electron pair-donating group or such an electron pair-donating group. The electron pair-donating group can be electrically neutral or negative and usually contains atoms such as O, N, P or S. The electron pair-donating group is a primary, secondary or tertiary amine group or an amide group, a nitrile group, an iso Nitrile group, cyanate group, isocyanate group, thiocyanate group, isothiocyanate group, azide group, thio group, thiolate group, sulfide group, sulfinate group, sulfonate group, phosphate group, phosphine group, Phosphite groups, hydroxyl groups, alcoholate groups, phenolate groups, ether groups, carbonyl groups and carboxylate groups, including but not limited to. Groups that can be converted to electron pair-donating groups include, for example, carboxylic acid, carboxylic anhydride and glycidyl groups. Specific examples of suitable volatile capping agents include ammonia, methyl amine, ethyl amine, butylamine, tetramethylethylene diamine, acetonitrile, ethyl acetate, butanol, pyridine, ethanethiol, tetrahydrofuran, and diethyl ether This is not restrictive. Preferably, the volatile capping agent is acetonitrile, butylamine, tetramethylethylene diamine, or pyridine.

Although the solvent and possibly dispersant are typically removed from the composition or ink herein by drying that occurs during film formation, the film as formed herein can be annealed by heating. Heating the film as formed herein typically provides a solid layer at a much lower temperature than the corresponding layer of microparticles, which may be caused in part by greater surface area contact between the particles. In any case, a suitable temperature for annealing the film as formed herein is about 100 ° C. to about 1000 ° C., more preferably about 200 ° C. to about 600 ° C., and even more preferably about 375 ° C. to about 525 ° C. And from about 375 ° C. to about 525 ° C. are stable temperature ranges for processing on aluminum foil or high melting point polymer substrates. The film to be annealed can be heated and / or accelerated through a heat treatment technique using at least one of the following procedures: pulsed thermal processing, exposure to a laser beam, or heating and / or similar through an IR lamp. Or related process. Other devices suitable for rapid heat treatment also include pulsed lasers, continuous wave lasers (typically 10 W to 30 W), pulsed electron beam devices, scanning electron beam systems and other beam systems, graphite plate heaters, lamps used in adiabatic methods for annealing. System, and a scanned hydrogen flame system. Non-direct low density systems can also be used. Alternatively, other heating procedures suitable for use herein include pulsed heating processes described in US Pat. Nos. 4,350,537 and 4,356,384; Pulsed electron beam treatment and rapid heat treatment as described in US Pat. Nos. 3,950,187, 4,082,958 and 4,729,962, each of which is incorporated herein by reference as a part thereof for all purposes. The heating methods described above may be applied singly, in a single or multiple combination with each other, and with the above or other similar processing techniques.

The annealing temperature can be adjusted to move back and forth within the temperature range without being maintained at a particular plateau temperature. This technique, referred to herein as rapid thermal annealing, or RTA, is particularly suitable for forming photovoltaic active layers (often referred to as "absorbent" layers) on metal foil substrates such as, but not limited to, aluminum foil. Details of this technique are described in US patent application Ser. No. 10 / 943,685, which is incorporated herein by reference in its entirety for all purposes.

The annealed film can have an increased density and / or reduced thickness compared to the density and / or thickness of the wet precursor layer because the carrier liquid and other materials have been removed during the treatment. In one embodiment, the film may have a thickness in the range of about 0.5 microns to about 2.5 microns. In other embodiments, the film may have a thickness of about 1.5 microns to about 2.25 microns. Treatment of the deposited layer of the composition or ink will fuse with the nanoparticles together and in most cases will remove the void space and thus reduce the thickness of the resulting dense film.

Sodium may be incorporated into a composition or ink of CZTS nanoparticles as provided herein to improve the quality of a film formed therefrom. In a first method, in a multilayer film as formed on a substrate, one or more layers of sodium containing material may be formed at the top and / or bottom of the layer as formed from its nanoparticles. Formation of the sodium-containing layer may occur by solution coating and / or other techniques, including but not limited to sputtering, evaporation, CBD, electroplating, sol-gel based coating, spray coating, CVD, PVD, ALD, and the like. . Optionally, in the second method, sodium may also be incorporated into the stack of layers in the film by sodium doping the CZTS nanoparticles in the film formed therefrom. Optionally, in a third method, sodium can be incorporated into the ink itself of the nanoparticles. For example, the ink may include sodium compounds with organic or inorganic counter ions (such as sodium sulfide), where the sodium compounds added into the ink (as individual compounds) will be present or dissolved as particles. Thus, sodium may be present in one or both of the “aggregate” form and the “molecularly dissolved” form of the sodium compound (eg dispersed particles).

The three above mentioned methods are not mutually exclusive and each is applied singly or in any single or multiple combinations with the other (s), so that the laminate containing the CZTS film contains the desired amount of sodium. Can provide. In addition, sodium and / or sodium-containing compounds may be added to the substrate (eg, into the molybdenum target). The source of sodium is not limited and may include one or more of the following: any deprotonated alcohol, wherein the proton is replaced by sodium, any deprotonated organic acid or inorganic acid, wherein the proton Is replaced by sodium, sodium hydroxide, sodium acetate, and sodium salts of the following acids: butanoic acid, hexanoic acid, octoanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and the like. Other sources include sodium halides such as sodium fluoride; Other alkali metals such as K, Rb or Cs can also be used as dopants with similar effects.

In addition, the sodium material may be combined with other elements that may provide a bandgap expansion effect, such as Al, Ge, and Si. In addition to sodium, the use of one or more of these elements may further improve the quality of the absorbent layer. The use of sodium compounds such as Na ₂ S or the like provides both Na and S to the film and is driven using annealing as provided by the RTA step to give a layer having a bandgap different from the bandgap of the unmodified CZTS layer or film. Could provide.

In yet another embodiment of the invention, the CZTS film may be formed on a substrate comprising a source of extra chalcogen in powder form, for example, containing chalcogen particles or binary chalcogenide particles. . Additional sources of chalcogens may be provided as separate layers containing additional sources of chalcogens, or additional sources of chalcogens may be incorporated into CZTS compositions or inks in which a single layer is printed on a substrate. Chalcogen particles may be micron- or submicron-sized non-oxygen chalcogen (eg Se, S) particles and may have a longest dimension that is less than a few hundred nanometers or several microns in size. Chalcogenide particles may be micron- or amacrone-sized, and may be group IB-2 membered chalcogenide nanoparticles such as (CuS, Se) and / or group IIA non-oxide chalcogenide nanoparticles such as Zn (Se, S) and / or Group IVA binary chalcogenide nanoparticles such as Sn (Se, S) ₂ . Other suitable chalcogen particles or binary chalcogenide particles include those selected from the group consisting of: non-oxygen chalcogen particles, group IB-2 member chalcogenide nanoparticles, group IIA non-oxide chalcogenide nanoparticles , Se particles, S particles, CuS particles, CuSe particles, ZnSe particles, ZnS particles, SnSe ₂ particles, SnS ₂ particles, and mixtures thereof.

To add a source of additional chalcogens, a mixture of the quaternary chalcogenide nanoparticles and additional chalcogen particles herein is placed on a substrate and heated to a temperature sufficient to melt the additional chalcogen particles to form liquid chalcogens. do. Liquid chalcogens and quaternary nanoparticles are heated to a temperature sufficient to react liquid chalcogens with nanoparticles to compensate for any chalcogen deficiency in the resulting film and densify the layer. Next, the film is cooled.

In some embodiments, a layer of chalcogen particles or binary chalcogenide particles may be formed at the bottom of the CZTS film. This position of the layer still allows the chalcogen particles to provide sufficient excess chalcogen or other deficient element to the CZTS layer, thus fully reacting and correcting the stoichiometric quaternary particles herein. In addition, since the chalcogen released from the underlying layer can increase through the CZTS film, this location of the layer can be advantageous to generate greater intermixing between the elements. The thickness of the chalcogen-rich layer may be in the range of about 0.4 microns to 0.5 microns. In yet another embodiment, the thickness of the chalcogen-rich layer is about 500 nm to 50 nm. In yet another embodiment thereof, multiple layers of material can be printed and reacted with chalcogen to vary ranges prior to deposition of the next layer, in which the graded composition content is added to the groups of layers that make up the multilayer film. Can be provided over.

Binary chalcogenide particles can be obtained starting from binary chalcogenide raw materials, for example particles of micron size or larger. Binary chalcogenide raw materials can be ball milled to produce particles of the desired size. Binary alloy chalcogenide particles may alternatively be formed by pyrometallurgy, or by melting elemental components and spraying the melt to form droplets that solidify into nanoparticles.

Chalcogen particles may be larger than binary chalcogenide nanoparticles and quaternary chalcogenide nanoparticles because the chalcogen particles melt before the binary and quaternary nanoparticles and provide good contact with the material. Preferably, the chalcogen particles are smaller than the thickness of the chalcogenide film formed. Chalcogen particles (eg, Se or S) can be formed in many different ways. For example, Se or S particles can be formed into commercially fine mesh powders (eg, 200 mesh / 75 microns) and ball milled to form the desired size. Se or S particles may alternatively be formed using an evaporation-condensation method. Alternatively, the Se or S raw material may be melted and sprayed (“particulate”) to form droplets that solidify into nanoparticles.

Chalcogen particles are also described in Wang and Xia in Nano Letters, 2004 Vol. 4, No. 10, 2047-2050 ("Bottom-Up and Top-Down Approaches to Synthesis of Monodispersed Spherical Colloids of Low Melting-Point Metals"), such as the "top-down" method as described. It can be formed using technology. This technique allows the treatment of elements with melting points below 400 ° C. as monodisperse spherical colloids, the diameter being adjustable from 100 nm to 600 nm and present in large amounts. In this technique, chalcogen (Se or S) powder is added directly to a boiling point organic solvent such as di (ethylene glycol) and melted to produce large droplets. After the reaction mixture is vigorously stirred and therefore emulsified for 20 minutes, a homogeneous spherical colloid of metal as the hot mixture is poured into a cold organic solvent bath (e.g. ethanol) to solidify the chalcogen (Se or S) droplets. Is obtained.

In yet another embodiment thereof, the electronic device can be fabricated from a film and include multiple layers; The first layer may contain a plurality of nanoparticles as described above and the second layer may contain binary semiconductors, chalcogen sources, sodium-containing materials, or mixtures thereof. In such a device, the first layer may be adjacent to the second layer.

Films fabricated on substrates as described above can be incorporated into electronic devices to act as absorbent layers, for example, in photovoltaic devices, modules, or solar panels. Typical solar cells include a transparent substrate (eg soda lime glass), a back contact layer (eg molybdenum), an absorber layer (also called a first semiconductor layer), a buffer layer (eg CdS; also a second semiconductor layer). ), And an upper electrical contact. The solar cell may also include electrical contacts or electrode pads on the top contact layer, and may include an anti-refractive (AR) coating on the front surface of the substrate to promote initial transmission of light into the semiconductor material. have. 3 illustrates this feature in the laminate shown herein containing the following elements: a transparent substrate 1; Back contact layer 2; Absorber layer 3 (formed from p-type CZTS / Se nanoparticles herein); Buffer layer 4; Top contact layer 5 (which may be, for example, a transparent conductive oxide (“TCO”) such as zinc oxide doped with aluminum); And electrical contacts or electrode pads 6 on the upper contact layer.

The substrate may be, for example, a metal foil such as titanium, aluminum, stainless steel, molybdenum, or a plastic or polymer such as polyimide (PI), polyamide, polyetheretherketone (PEEK), polyethersulfone (PES), poly It may be made of etherimide (PEI), polyethylene naphthalate (PEN), polyester (PET), or metalized plastic. The base electrode may be made of an electrically conductive material, such as an Al foil layer, for example from about 10 microns to about 100 microns thick. Any interfacial layer can facilitate the bonding of the electrode to the substrate. Adhesion may be made of various materials, including but not limited to chromium, vanadium, tungsten and glass, or compounds such as nitrides, oxides and / or carbides. The CZTS absorbent layer may be about 0.5 microns to about 5 microns thick after annealing, and more preferably about 0.5 microns to about 2 microns thick after annealing.

N-type semiconductor thin films (sometimes referred to as junction partner layers) are, for example, inorganic materials such as cadmium sulfide (CdS), zinc sulfide (ZnS), zinc hydroxide, zinc selenide (ZnSe), n-type organic materials, or Some combinations of two or more of these or similar materials, or organic materials such as n-type polymers and / or small molecules. The layers of these materials may be, for example, from about 2 nm to about 1000 nm, more preferably from about 5 nm to about 500 nm, by chemical vapor deposition (CBD) and / or chemical surface deposition (and / or related methods), And most preferably at a thickness ranging from about 10 nm to about 300 nm. It may also be arranged for use in continuous roll-to-roll and / or split roll-to-roll and / or batch systems.

The transparent electrode may comprise a transparent conductive oxide layer such as zinc oxide (ZnO), aluminum doped zinc oxide (ZnO: Al), indium tin oxide (ITO), or cadmium stannate, any of which may be sputtered, And may be deposited using any of a variety of means including but not limited to evaporation, CBD, electroplating, CVD, PVD, ALD and the like.

Alternatively, the transparent electrode may comprise a transparent conductive polymeric layer, such as a transparent layer of doped PEDOT (poly-3,4-ethylenedioxythiophene), which may be deposited using spin, dip, or spray coating or the like. . PSS: PEDOT is a doped conductive polymer based on a heterocyclic thiophene ring crosslinked by a diether. The water dispersion of PEDOT doped with poly (styrenesulfonate) (PSS) is described in H. C. Starck of Newton, Mass. under the trade name of Baytron® P]. The transparent electrode may further comprise a layer of metal (eg Ni, Al or Ag) fingers to reduce the overall sheet resistance. Alternatively, the transparent conductor layer can include carbon nanotube-based transparent conductors.

The manipulations and effects of certain embodiments of the present invention can be more fully understood from the series of examples as described below. The embodiments on which these examples are based are merely representative, and the selection of these embodiments to illustrate the invention is based on the materials, components, reactants, batches, designs, conditions, specifications, steps, techniques not described in the examples. It is not intended that the subject matter not suitable for use herein or described in the examples be excluded from the scope of the appended claims and their equivalents.

Example

matter

Copper chlorite, Cu (I) Cl 99.99%; Zinc chloride, ZnCl ₂ 99.99%; Stannous chloride, 99.99% SnCl ₂ , elemental sulfur, elemental selenium, thiourea, toluene, p-xylene, acetonitrile and chloroform were all purchased from Aldrich and used without further purification. Oleylamine (70% industrial grade) was purchased from Fluka and filtered through a 0.45 μm filter (Whatman GE). Elbasite® 2028 and Elbasite® 2008 were obtained from Lusite International, Inc. (Cordova, TN, Tennessee, USA).

General procedure for the manufacture of solar cells

Mo-sputtered substrate. Substrates for solar cells were made by coating a soda lime glass substrate with a 500 nm layer of patterned molybdenum using a Denton Sputtering System. The deposition conditions were 150 watts DC power, 20 sccm Ar, and 0.67 Pa (5 mT) pressure.

Cadmium sulfide deposition.

Precursor solutions for CdS baths were prepared according to Table 1 and combined at room temperature in a reaction vessel containing the prepared substrates such that the substrates to be coated were completely submerged. Immediately after mixing the precursor solution, the vessel containing the mixed components was placed in a water-heated vessel (65 ° C.) (large crystallization dish). CdS was deposited on the sample for 17.5 minutes. Samples were washed in deionized water for 1 hour and dried at 200 ° C. for 15 minutes.

Transparent conductor deposition.

Transparent conductors were sputtered on top of CdS with the following structures: 500 nm Al-doped ZnO and 50 using 2% Al ₂ O ₃ , 98% ZnO target (75 W RF, 0.13 Pa (10 mTorr), 20 sccm) Nm ZnO (150 W RF, 0.67 Pa (5 mTorr), 20 sccm).

Example 1

Synthesis of Copper Zinc Tin Sulfur Nanoparticles Using Continuous Addition of Precursor at 30 ° C Reaction Temperature

In the following procedure, all metal salts and elemental sulfur were dissolved in oleylamine at 100 ° C .: 80 mg (0.586 mmol) solution of zinc chloride dissolved in 10 ml oleylamine and dissolved in 10 ml oleylamine. A solution of 102 mg (0.587 mmol) of ditin chloride was mixed with stirring in a flask already degassed and heated to 110 ° C. under Ar atmosphere. After 5 minutes of stirring, a solution of 77 mg (0.777 mmol) of copper chlorite dissolved in 10 ml of oleylamine was added to the reaction mixture, and the resulting solution was stirred for an additional 5 minutes. At this point, a solution of 163 mg (5.08 mmol) of sulfur dissolved in 10 ml of oleylamine was added to the system and the reaction temperature was raised to 230 ° C. at a rate of 10 ° C./min.

After reaching 230 ° C., the system was held at this temperature for 10 minutes and then the heating was stopped. The reaction was allowed to cool naturally with stirring while allowing the heating block to remain in place while cooling. After cooling, 80 ml of ethanol were added to the reaction mixture. The particles were collected by centrifugation and the solvent was decanted. The presence of the casterite structure was measured by XRD and the ratio of Cu: Zn: Sn: S was measured via ICP (see Table 2). Particle size was measured using DLS, TEM (see FIGS. 1-1, 1-2, 1-3, 1-4) and AFM. The particle size ranged from 1 nm to 10 nm.

Example 2

Synthesis of Copper Zinc Tin Sulfur Nanoparticles Using Continuous Addition of Precursor at 160 ° C Reaction Temperature

In the following procedure, all metal salts and elemental sulfur were dissolved in oleylamine at 100 ° C .: a solution of 80 mg (0.586 mmol) of zinc chloride dissolved in 10 ml of oleylamine and 102 dissolved in 10 ml of oleylamine A solution of mg (0.587 mmol) of ditin chloride was mixed with stirring in a flask already degassed and heated to 160 ° C. under Ar atmosphere. After 5 minutes of stirring, a solution of 77 mg (0.777 mmol) of copper chlorite dissolved in 10 ml of oleylamine was added and the three components were stirred for an additional 5 minutes. At this point, a solution of 163 mg (5.08 mmol) of elemental sulfur dissolved in 10 ml of oleylamine was added to the system, while the reaction temperature was maintained at 160 ° C. for an additional 10 minutes. The heating was then stopped and the reaction allowed to cool naturally under stirring while allowing the heating block to remain in place while cooling. Upon cooling, 40 ml of a 1: 1 mixture of hexane and ethanol were added to the reaction mixture. The particles were collected via centrifugation and the solvent was decanted. The presence of the casterite structure was measured by XRD and the ratio of Cu: Zn: Sn: S was measured via EDX (see Table 2). Particle size was measured using DLS, TEM (FIG. 2) and AFM. The particle size ranged from 10 nm to 50 nm.

Example 3

Synthesis of Copper Zinc Tin Selenium Nanoparticles Using Continuous Addition of Precursors

In the following procedure, all metal salts and elemental selenium were dissolved in oleylamine at 100 ° C .: Elemental sulfur was replaced with elemental selenium 401 mg (5.08 mmol) after the procedure of Example 1. The presence of the casterite structure was measured by XRD.

Example  4

Synthesis of Copper Zinc Tin Sulfur Nanoparticles Using Simultaneous Addition of Precursors

In the following procedure, all metal salts and elemental sulfur were dissolved in oleylamine at 100 ° C .: 80 mg (0.586 mmol) solution of zinc chloride dissolved in 10 ml oleylamine, dissolved in 10 ml oleylamine 102 mg (0.587 mmol) solution of ditin tin chloride, 77 mg (0.777 mmol) solution of copper chlorite dissolved in 10 ml oleylamine, and 163 mg (5.08) dissolved in 10 ml oleylamine A solution of elemental sulfur) was simultaneously mixed and the reaction temperature was raised to 230 ° C. at a rate of 10 ° C./min. After reaching 230 ° C., the system was held at this temperature for 10 minutes and then the heating was stopped. The reaction was allowed to cool naturally with stirring while allowing the heating block to remain in place while cooling. After cooling, 80 ml of ethanol were added to the mixture. The particles were collected by centrifugation and the solvent was decanted. The particle size ranged from 10 nm to 50 nm and the composition exhibited a Zn: Sn ratio of 1: 2 in CZTS. The presence of the casterite structure was measured by XRD and the ratio of Cu: Zn: Sn: S was measured via EDX (see Table 2). Particle size was measured using DLS, TEM and AFM. Different compositions were obtained while maintaining similar XRD patterns.

Comparative example  5

Nanoparticle Synthesis Using Thiourea as Sulfur Source

Stir vigorously a mixture of 0.1 g copper chlorite (1 mmol Cu), 0.068 g zinc chloride (0.5 mmol Zn), 0.094 g zinc ditin (0.5 mmol Sn), and 10 ml oleylamine And degassed in a Schlenk flask for 30 minutes at 60 ° C. by drawing a vacuum using a Schlenk line. The mixture is then heated to 130 ° C. for 10 minutes under nitrogen. During heating, the solution turns from blue to yellow, indicating the formation of oleylamine complexes of Cu, Zn and Sn. On the other hand, thiourea solutions are prepared by dissolving 0.076 g of thiourea (1.0 mmol) in 1 ml of oleylamine at 200 ° C. under nitrogen in a Schlenk flask. The Zn / Sn / Cu / oleylamine reactant solution is cooled to 100 ° C. and the thiourea reactant solution is added via cannula. Immediately after injection, the reaction mixture is heated to 240 ° C. at a rate of 15 ° C./min. After 1 hour, the Schlenk flask containing the nanocrystals is removed from the heating mantle and allowed to cool to room temperature. Next, ethanol (30 mL) is added to precipitate the nanocrystals, followed by centrifugation at 7000 rpm for 3 minutes. The supernatant is decanted from the nanocrystals and discarded. Nanocrystals are redispersed in various nonpolar organic solvents, including chloroform, hexane, and toluene. Prior to characterization, the dispersion is centrifuged again, typically at 7000 rpm for 5 minutes to remove improperly capped nanocrystals. Samples were characterized via XRD and EDAX (see Table 2). XRD results reveal the presence of SnS, ZnS, Cu2S. The small amount of Zn detected by EDAX reflects that this process used to synthesize other types of chalcogenide-containing materials cannot be estimated for CZTS synthesis.

Example 6

Preparation of CZTS Inks in Toluene

Inks were prepared by redispersing 0.086 g of CZTS nanoparticles prepared by the procedure of Example 1. The particles were dispersed via ultrasonic waves in 1 ml of toluene (density 0.8669 g / ml) to generate an ink having a nanoparticle concentration of 10% by weight.

Example 7

Preparation of CZTS Inks in p-Xylene Using Elbasite® 2028 Binder

Ink was prepared by the following steps: First, 0.172 g of CZTS nanoparticles prepared by the procedure of Example 1 were dispersed by ultrasonication in 1 ml of p-xylene (density 0.861 g / ml) by nanoparticles. A 20 wt% suspension of was generated. Next, the nanoparticle suspension was mixed with 1 ml of a solution of 2% by weight of Elbasite® 2028 p-xylene to generate an ink with 10% by weight of nanoparticles.

Example 8

Preparation of CZTS Ink in Toluene Using Elbasite® 2028 Binder

Ink was prepared by the following steps: First, 0.172 g of CZTS nanoparticles prepared by the procedure of Example 1 were dispersed by ultrasonication in 1 ml of toluene (density 0.861 g / ml) to obtain 20 nanoparticles of nanoparticles. A weight percent suspension was generated. Next, the nanoparticle suspension is eluted at 2% by weight in toluene? Mixing with 1 ml of a solution of 2028 resulted in an ink with nanoparticles of 10% by weight density.

Example 9

Elbasite ？ 2008 binder In acetonitrile CZTS Manufacture

Ink was prepared by the following steps: First, 0.172 g of CZTS nanoparticles prepared by the procedure of Example 1 were dispersed by ultrasonication in 1 ml of acetonitrile (density 0.786 g / ml) to obtain nanoparticles. A 20 wt% suspension was generated. Next, the nanoparticle suspension was eluted with 2% by weight elbasite in acetonitrile? Mix with 1 ml of 2008 solution to generate ink with 10% by weight nanoparticles.

Example 10

CZTS Nanoparticle Synthesis: Exchange of Oleylamine to Butylamine

CZTS nanoparticles were prepared according to the procedure of Example 1, redispersed in toluene, centrifuged and the solvent decanted. The pellets were dried under vacuum. The dry material was then weighed and then 0.3 g of material was placed in a round bottom flask equipped with a stir bar under Ar atmosphere. Anhydrous butyl amine (5 mL) was added to the flask using a syringe and the reaction was left to stir for 3 days at room temperature, yielding ink in butylamine. The particles were then precipitated by addition of 15 ml of ethanol, collected via centrifugation, and the solvent decanted to give nanoparticle pellets.

Example 11

Preparation of Butylamine-Capped CZTS-Nanoparticle Inks in Chloroform

The nanoparticle pellets prepared according to Example 10 were redispersed in chloroform at a concentration of 150 mg / ml and then filtered through a 0.22 μm polytetrafluoroethylene filter to generate ink.

Example 12

Formation of CZTS Film

The wet pellet (˜100 mg) of CZTS prepared according to Example 1 was dissolved in 0.5 ml of toluene to give a fluid suspension. The suspension was sonicated for 5 to 60 minutes using a Branson 25-10 sonicator in a 5 minute step. The highest quality dispersion was obtained using a sonication time of 30 to 45 minutes.

Next, using a Speed-line Technologies 3GP benchtop spin-coater, the specimen was spin-coated onto a glass substrate and also molybdenum-coated of the glass substrate patterned with sputtered molybdenum It was also spin-coated on the surface. The coating speed ranged from 500 rpm to 1500 rpm and the coating time ranged from 10 seconds to 30 seconds. The highest quality coatings were obtained for 1000-rpm, 20-second spin conditions. The thickness of the resulting film varied from 50 nm to 800 nm.

The film was then annealed in a furnace or rapid thermal annealing processor. The annealing temperature ranged from 400 ° C. to 550 ° C. and the time varied from 10 minutes to 30 minutes. The highest quality annealed film was obtained by annealing at a temperature of 500 ° C. to 550 ° C. for 15 minutes. Film thickness and roughness were obtained using a profilometer and the film was further characterized by optical spectra. MILA-5000 Infrared Lamp Heating System by ULVAC-RICO Inc. (Methuen, Mass., USA) for rapid thermal annealing Heating System) was used for heating, and the system was cooled using a fixed Polyscience (Niles, IL, USA) recycle bath at 15 ° C. Samples were heated under a nitrogen purge as follows: 20 ° C. for 10 minutes; Ramp to 400 ° C. in 1 minute; Fixation at 400 ° C. for 2 minutes; Cool back to 20 ° C. for approximately 30 minutes.

Example 13

Densification of CZTS Films by Wetting with Ethanol

Pre-annealed films were prepared as described in Example 12. After coating these films were placed on a spin coater and then wetted with ethanol. After soaking for a few seconds, the spin program was run again to help dry the film. The resulting film was denser and harder than the pre-soaked film.

Example 14

Formation of Bar-Coated CZTS Films

Wet pellets (approximately 100 mg) of CZTS prepared according to Example 1 were dissolved in approximately 0.5 ml of various solvents, including toluene and chloroform, to obtain an ink. The resulting CZTS ink was bar-coated on a glass substrate. Two of the bar-coated films were annealed in a furnace at 550 ° C. for 15 minutes. The film was characterized via XRD, some of the film was scraped off and analyzed via HR-TEM.

Example 15

Solar Cells with Spin-Coated CZTS Nanoparticle-Induced Absorber Layers

An annealed film of p-type CZTS absorbent on Mo-sputtered soda lime glass was prepared as described in Example 12. The specimen was then placed in a CdS bath and about 50 nm of n-type CdS was deposited on top of the CZTS film. The transparent conductor was then sputtered on top of the CdS. The completed device was tested under 1 solar illumination and the J-V feature is illustrated in FIG. 4.

Example  16

CZTS-Based Solar Cells on Polyimide Substrates with Thermally Evaporated Sodium Layer

Solar cells are fabricated using a CZTS absorber layer using a high temperature polyimide film as the substrate. After the procedure of Example 15, the modification is provided to provide some of the sodium needed for a high performance solar cell, and a very thin layer of Na (<1 nm) is thermally evaporated on Mo. Next, the CZTS ink is coated onto the polyimide / Mo / Na substrate.

Example  17

Solar Cells on Polyimide Substrates Fabricated from Sodium-Doped CZTS Inks

Solar cells are fabricated using a CZTS absorber layer using a high temperature polyimide film as the substrate according to the procedure of Example 15. Sodium octanoate is incorporated into the ink at 0.5% by weight.

Example  18

CZTS ink doped with elemental chalcogen

Ink of CZTS nanoparticles is formed according to the procedure of Example 6. Amacron-sized elemental sulfur particles are added to the ink at 1% by weight while sonicating. A solar cell is prepared using this ink according to the procedure of Example 15.

Example  19

CZTS ink doped with binary chalcogenide particles

Ink of CZTS nanoparticles is formed according to the procedure of Example 6. Binary chalcogenide nanoparticles of SnS ₂ and ZnS are added to the ink at 0.2% by weight, respectively, with sonication. Using this ink, the coating and solar cell were prepared according to the procedure of Example 15.

Examples 20-25

Coatings and solar cells based on various CZTS inks

Ink of CZTS nanoparticles is formed according to the procedures listed in Table 3. Using these inks, the coating and solar cell were prepared according to the procedure of Example 15.

Example 26

Modifications in CZTS Compositions: Sulfur Gradient

Ten inks of CZTS nanoparticles doped with elemental sulfur were formed according to the procedure of Example 18, and the weight percent sulfur in the ink varied from 1.0 weight percent to 0.1 weight percent in steps of 0.1 weight percent. A CZTS film with a sulfur gradient is prepared on Mo-sputtered soda lime glass by spray-coating CZTS ink in continuous spray passes using the ink composition for each layer as shown in Table 4. Using this absorbent layer, a solar cell is fabricated according to the procedure of Example 15.

Example 27

Modifications in CZTS Compositions: Cu-Poor with Cu Gradients

Ten inks of CZTS nanoparticles doped with binary chalcogenide nanoparticles of SnS ₂ and ZnS were formed according to the procedure of Example 19, and the weight percentage of binary chalcogenide nanoparticles in the ink was 0.05% by weight. Steps vary from 0% to 0.45% by weight. A low copper CZTS film in a copper gradient is prepared on Mo-sputtered soda lime glass by spray-coating CZTS ink in a continuous spray pass using the ink composition for each layer as shown in Table 4. Using this absorbent layer, a solar cell is fabricated according to the procedure of Example 15.

Example 28

Spray-Coating of CZTS Nanoparticles

CZTS nanoparticles (100 mg) were prepared according to the procedure of Example 1. The nanoparticles were suspended in 5 ml of chloroform and then the suspension was sonicated for 10 minutes prior to deposition. The ink was sprayed onto Mo-sputtered soda lime glass according to the conditions given in Table 5. Using this absorbent layer, a solar cell is fabricated according to the procedure of Example 15.

Example 29

Insulating ZnO Window

The solar cell was fabricated according to the procedure of Example 15 using insulating ZnO as the window instead of CdS.

Example 30

CZTS  Absorbent layer and

Solar Cells with Carbon Nanotube-Based Transparent Conductors

Solar cells are fabricated according to the procedure of Example 15 using carbon nanotube-based transparent conductors instead of ZnO: Al.

Example 31

CZTS nanoparticles synthesized by electromagnetic radiation

In the following procedure, all metal salts and elemental sulfur are dissolved in oleylamine at 100 ° C .: 80 mg (0.586 mmol) solution of zinc chloride dissolved in 5 ml oleylamine, 102 dissolved in 5 ml oleylamine. Mg (0.587 mmol) solution of ditin tin chloride, solution of 77 mg (0.777 mmol) copper chlorite dissolved in 5 ml oleylamine and 163 mg (5.08 mmol) dissolved in 5 ml oleylamine A solution of elemental sulfur of was simultaneously mixed and loaded into a special vial equipped with an electromagnetic wave synthesizer equipped with a stirring rod. The vial is then loaded into an Initiator-8 microwave (Biotage, Sweden) with a heat set point of 230 ° C. After reaching 230 ° C., the system is held at this temperature for 10 minutes and then the vial is removed from the system. After cooling in the rack for 30 minutes, the vial is opened and the reaction mixture is delivered as equal volumes (20 ml each) into two 50 ml Falcon test tubes. Next, 20 mL volume of ethanol is added to each tube. The particles are collected by centrifugation and the solvent is decanted.

Example 32

Sulfurization of CZTS Film

CZTS nanoparticles were prepared according to the procedure of Example 1. Wet pellets (approximately 100 mg) of CZTS prepared according to Example 1 were suspended in approximately 0.5 ml of various solvents, including toluene and chloroform, to obtain an ink. The resulting CZTS ink was bar-coated on a glass substrate. The bar-coated film was annealed in the furnace for 1 hour at 500 ° C. under rich sulfur atmosphere and under continuous flow of nitrogen atmosphere. Annealing was carried out in a single-zone Lindberg / Blue (Lindberg / Blue (Ashville, NC)) tube furnace equipped with an external thermostat and a 5.1 cm (2 inch) quartz tube. The coated substrate was placed on a quartz plate inside the tube. A 7.6 cm (3 inch) long ceramic boat was loaded with 2.5 g of elemental sulfur and placed near the nitrogen inlet outside the direct heating zone.

Example 33

Seleniumization of CZTS Films

CZTS nanoparticles are prepared according to the procedure of Example 1. Wet pellets (approximately 100 mg) of CZTS prepared according to Example 1 were suspended in approximately 0.5 ml of various solvents, including toluene and chloroform, to obtain an ink. The resulting CZTS ink is bar-coated on a glass substrate. The bar-coated film is annealed in the furnace for 1 hour at 500 ° C. under a rich selenium atmosphere and under a continuous flow of nitrogen atmosphere. 12.7 cm (5 ") L x 3.6 cm (1.4") W x 2.5 cm (1 ") with 0.3 cm (1/8") wall with 1 mm hole and lid with lip in center Placed in a H graphite box (customized to Industrial Graphite Sales, Harvard, IL), Harvard, Illinois, USA. Each graphite box contains 0.1 g of selenium, two small ceramic boats (2.50 cm (0.984 ") L x 1.50 cm (0.591") W x 0.50 cm (0.197 ") H at each end The graphite box is then placed in a 5.1 cm (2 inch) tube and there are no more than two graphite boxes per tube, vacuum is applied to the tube for 10 to 15 minutes, followed by 10 to 15 minutes. The purge process is carried out three times, and then the tube containing the graphite box is heated at 500 ° C. for 1 hour in a single-zone furnace where both heating and cooling are carried out under nitrogen purge. Outgoing gas is sparged through a continuous bubbler: 1 M NaOH (aq) followed by 1 M Cu (NO 3) 2 (aq).

When a range of numerical values is mentioned or established herein, the range includes the endpoint and all individual integers and fractions within that range, and also to form a subgroup of a larger group of values within the stated range. Each of the narrower ranges formed therein by the end points and all possible various combinations of integers and fractions inside includes the same extent as if each of these narrower ranges were explicitly mentioned. When a range of numerical values is described herein as being greater than the stated values, the ranges are nevertheless finite, and the ranges are defined at their upper limits by values operable within the context of the invention disclosed herein. Boundaries are made. If a range of numerical values is described as being less than the stated value, then the range is nevertheless bounded by the nonzero value at the lower end of the range.

In this specification, unless specifically indicated otherwise by the context of the use, amount, size, range, formulation, parameters, and other amounts and features recited or referred to herein, and unless specifically modified by the term "about", It may not be necessary, and may also be larger or smaller (if necessary) than roughly mentioned and / or mentioned, which is within the context of the present invention as well as tolerances, conversion factors, rounding, measurement errors, etc. Reflecting a value that is operatively and / or operatively corresponding to the stated value.

In this specification, an embodiment of the subject matter of this disclosure includes, originates, contains, has, consists of, or is made of, or otherwise incorporates, certain features or elements, unless expressly stated otherwise or contrary to the context of use. When described or described as being constructed, one or more features or elements may be present in the embodiments in addition to those explicitly described or described. However, alternative embodiments of the present subject matter may be described or described as consisting essentially of certain features or elements, where features or elements that significantly change the operating principle or distinctive features of the embodiments are provided. It does not exist in the embodiment. Additional alternative embodiments of the present subject matter may be described or described as consisting of certain features or elements, in which only those features or elements are specifically described or described. do.

Claims (20)

A quaternary nanoparticle comprising copper, zinc, tin, chalcogen, and a capping agent, wherein the chalcogen is selected from the group consisting of sulfur, selenium, and mixtures thereof. The nanoparticle of claim 1 having a longest dimension of about 1 nm to about 1000 nm, and / or a kesterite structure. The method of claim 1 wherein the molar ratio of copper to zinc to tin to chalcogen is about 2: 1: 1: 4, the molar ratio of copper to (zinc + tin) is less than 1, or the molar ratio of zinc to tin is greater than one. Nanoparticles. The process of claim 1, wherein the capping agent comprises: (a) an organic molecule comprising a nitrogen-, oxygen-, sulfur-, or phosphorus-based functional group; (b) Lewis bases; Or (c) a nanoparticle comprising an electron pair-donating group having a boiling point of less than about 150 ° C. at ambient pressure, or a group that can be converted to an electron pair-donating group. A composition comprising a plurality of nanoparticles according to claim 1, wherein the composition has a particle size distribution with an average longest particle dimension in the range of about 10 nm to about 100 nm and a standard deviation of about 10 nm or less. (a) forming a reaction mixture of (i) metal salts and / or complexes of copper, zinc and tin, (ii) one or more chalcogen precursor (s), and (iii) a first capping agent in a solvent, and (b) heating the reaction mixture to form nanoparticles, the method of producing copper-zinc-tin-chalcogenide quaternary nanoparticles. 7. The process according to claim 6, wherein the individual metal salts and / or complexes of copper, zinc and tin are separately added successively to the mixture of solvent and first capping agent to form a reaction mixture, and then the chalcogen precursor is added to the reaction mixture. . The method of claim 6, further comprising: (a) contacting the reaction mixture with a second capping agent having a greater volatility than the first capping agent to exchange the first capping agent with a second capping agent in the nanoparticles; Or (b) recovering the nanoparticles from the reaction mixture and then contacting the nanoparticles with a second capping agent having greater volatility than the first capping agent to exchange the first capping agent with a second capping agent in the nanoparticles. How to include. The method of claim 8, wherein the second capping agent has a boiling point of less than about 200 ° C. at ambient pressure. An ink comprising a composition comprising a plurality of nanoparticles according to claim 1 and an organic solvent. The method of claim 10, further comprising at least one binder or surfactant selected from the group consisting of degradable binders, degradable surfactants, cleavable surfactants, surfactants having a boiling point of less than about 250 ° C., and mixtures thereof. Ink. A composition comprising a plurality of nanoparticles according to claim 1, produced as a film. A method of forming a film, comprising depositing a layer of a composition comprising a plurality of nanoparticles according to claim 1 on a substrate, and drying the deposited layer of the composition to remove solvent therefrom. 15. The method of claim 13, further comprising heating the film in the atmosphere to anneal it, wherein the atmosphere is inert or selenium vapor, sulfur vapor, hydrogen, hydrogen sulfide, hydrogen selenide, and mixtures thereof. A method comprising a reactive component selected from the group consisting of. The method of claim 13, wherein the film comprises a first capping agent and the film is contacted with a second capping agent having greater volatility than the first capping agent to convert the first capping agent into the second capping agent in the nanoparticles of the film. Further comprising the step of exchanging. The method of claim 15, wherein the second capping agent has a boiling point of less than about 200 ° C. at ambient pressure. An electronic device comprising a film comprising a plurality of nanoparticles according to claim 1. The method of claim 17, wherein the film comprises multiple layers, the first layer comprises a plurality of nanoparticles according to claim 1, and the second layer is a binary semiconductor, a chalcogen source, a sodium-containing material, or An electronic device comprising the mixture. The chalcogenide source of claim 18, wherein the chalcogenide source is selected from the group consisting of chalcogen particles, binary chalcogenide particles, and mixtures thereof; The sodium-containing material is selected from the group consisting of sodium salts of deprotonated alcohols, sodium salts of deprotonated acids, sodium hydroxide, sodium acetate, sodium sulfide, and mixtures thereof. The electronic device of claim 18 wherein the first layer is adjacent to the second layer.

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